平板状SOFC结构热应力特性分析

本文对平板状固体氧化物燃料电池的热应力进行了分析,并对其结构建立了三维有限元计算模型,探讨了工作温度、电极厚度和电解质厚度、以及各层间的热膨胀系数差异对热应力的影响。仿真结果表明,热应力的最大值出现在电极与电解质界面处;降低电池工作温度有利于电极和电解质热应力的降低:热应力的大小和分布与电极材料的热膨胀系数、电极厚度和电解质厚度密切相关。     

固体氧化物燃料电池的热力学及电化学应用基础

固体氧化物燃料电池是一种典型的电化学装置,可以把燃料气和空气（或氧气）的化学能直接转化为电能。电池的整个反应过程可以根据还原剂和氧化剂反应自由焓来进行热力学计算。对于最简单的氢气和氧气的反应来说,可以根据可逆反应平衡方程式计算电池的可逆功,而且SOFC系统和外部环境的热交换也是可逆的。SOFC作为一种伴生热能的发电装置,对热力学的理解必不可少。所以本文将首先介绍一下SOFC的热力学基础,而作为一种电化学发电装置,需要系统了解SOFC的电化学基础,其中重点介绍SOFC的电化学分析曲线——i-V曲线。     

基于固体氧化物燃料电池的甲烷电化学部分氧化

合成气(H2和CO)是化工生产的重要原料,主要通过甲烷的重整或部分氧化获得,传统的甲烷重整制合成气的方法存在能耗高和催化剂失效等问题.固体氧化物燃料电池(SOFC)则通过传导氧离子的电解质将氧从阴极输送到阳极,实现位于阳极的甲烷的电化学氧化,调整电流电压的大小从而控制参与反应的氧气含量,可避免催化剂失效的问题并提升燃料...     

固体氧化物燃料电池/燃气轮机混合动力系统建模仿真研究进展

固体氧化物燃料电池(Solid Oxide Fuel Cell, SOFC)工作温度高,阳极可发生燃料内重整反应,具有较高的燃料灵活性,同时可与燃气轮机(Gas Turbine, GT)构成固体氧化物燃料电池/燃气轮机(SOFC/GT)混合动力系统进一步提高系统效率。SOFC/GT混合动力系统一般分为底层和顶层循环2种,考虑到SOFC/GT示范性工程有限且建造成本高,一般采用数学建模仿真方法开展SOFC/GT研究。与单独SOFC或GT模型不同,常采用热力学建模仿真对SOFC/GT系统性能进行分析优化。介绍了SOFC/GT混合动力系统常用热力学模型,并对目前SOFC/GT混合动力系统常见稳态和动态热力学建模工作展开综述,考虑到现阶段SOFC/GT混合动力系统多采用商业化软件(Aspen Plus、COMSOL、gPROMs等)建模,建模功能有限、不易拓展,后续工作可基于Matlab、Python等软件进行开源代码的编程;现阶段主要围绕系统级集总模型开展分析,无法准确描述燃料电池的局部特性,后续工作可在SOFC/GT建模中引入一维甚至更高维度的SOFC模型进一步提高建模精度。     

燃料电池固体氧化物电解质研究进展

本文对当前燃料电池用固体电解质材料的研究进展进行了综述.首先介绍了固体氧化物燃料电池的发展趋势及其与电解质材料性能的关系,然后分别对Y2O3稳定ZrO2(YSZ)、Sc2O3稳定ZrO2(ScSZ)、Ce基材料和其他一些电解质材料如Bi2O3、LaGaO3的制备、掺杂和电导率性能等方面进行了总结.最后,提出了今后电解质材料研的几个重要方向.     

固体氧化物燃料电池系统及其应用

对固体氧化物燃料电池系统和单体电池及其工作原理、材料组成等作了简要介绍,并介绍了固体氧化物燃料电池在电厂混合发电方面与燃气轮机组成的联合系统技术以及以天然气为燃料家庭热电联产方面的应用。并指出固体氧化物燃料电池由于其高效、环保清洁将是未来能源利用的主要方式。     

固体氧化物燃料电池的研究进展

固体氧化物燃料电池(SOFC)是先进陶瓷材料的一种重要应用,可以通过电化学反应将燃料的化学能直接转换为电能。SOFC具有效率高、性能稳定、便携、低污染等优点,可以实现能源的有效清洁利用。本文结合国内外SOFC的研究情况,分析讨论了SOFC的技术优势、地方产业优势及产业难题,并结合国家政策方面对我国SOFC产业的未来发展做了展望。     

固体氧化物燃料电池的变工况特性

以大面积电池和千瓦级电堆为研究对象,在确定的燃料成分、流量、和工作温度下,系统研究了电流阶梯变化、电流脉冲变化、电堆热启停以及冷热循环(冷启停)等工况下电堆的输出性能。结果表明:在小电流区域,电堆的电压和功率能够快速跟踪电流变化;在大电流区域,电池的电压出现波动和弛豫,电堆的功率也出现弛豫。热启停实验结果表明,SOFC电堆对电流的on-off变化具有足够的耐受性,一定数量的热启停不会导致电堆性能的明显衰减。而冷热循环会导致应力释放,引起接触电阻变化,从而使电堆性能衰减,5次以上热循环可使应力释放趋于缓和。     

平板型固体氧化物燃料电池的流场设计及优化概述

固体氧化物燃料电池(Solid Oxide Fuel Cells,SOFCs)具有燃料适用性广、余热利用价值高、能量转化效率高的优点,成为当下能量转化技术的研究热点.但是,在商业化之前,SOFCs仍然存在着一些亟待改善的问题,其中,稳定性和工作寿命便是最关键的问题.因为流场与温度场、电场相互耦合,不均匀的流场极易导致电...     

Current and voltage distributions in a tubular solid oxide fuel cell (SOFC)

One of the major obstacles to improving electrochemical performance of SOFCs is the limitation with respect to current collecting. The aim of this study is to examine these limitations on the basis of a model of a single cell of tubular SOFC. The simulation results allow us to understand and analyze the effects of ionic and electronic ohmic drops on cell performance. This paper describes a model using the CFD-Ace software package to simulate the behaviour of a tubular SOFC. Modelling is based on solving conservation equations of mass, momentum, energy, species and electric current by using a finite volume approach on 3D grids of arbitrary topology. The electrochemistry in the porous gas diffusion electrode is described using Butler-Volmer equations at the triple phase boundary. The electrode overpotential is computed at each spatial location within the catalyst layer by separately solving the electronic and ionic electric potential equations. The 3D presentation of the current densities and the electronic and ionic potentials allows analysis of the respective ohmic drops. The simulation results show that the principal limitations are at the cathodic side. The limitations due to ionic ohmic drops, classically considered to be the main restrictions, are confirmed. The particular interest of our study is that it also shows that, because of the cylindrical geometry, there is a significant electronic ohmic drop.     

Performance of an anode-supported tubular solid oxide fuel cell (SOFC) under pressurized conditions

An anode-supported tubular solid oxide fuel cell (SOFC) with a 15-μm thick YSZ electrolyte and an active area of 100 cm² was successfully fabricated by co-firing process, and the cell performance was measured under both atmospheric and pressurized conditions. The experimental results showed that the cell performance was significantly improved under the pressurized condition. When the pressure was increased from 1 to 6 atm, the maximum power density increased from 135.0 to 159.0 mW cm⁻² at 650 °C, and from 266.7 to 306.0 mW cm⁻² at 800 °C. The maximum power density at 800 °C and 4 atm was decreased from 334.8 to 273.9 mW cm⁻² when increasing the fuel utilization from 10% to 90%. Under the test condition of 70% fuel utilization, 800 °C and 4 atm, the cell could run stably at 0.7 V and 350 mA cm⁻² for 50 h, almost without any performance loss.     

Investigation of solid oxide fuel cell short stacks for mobile applications by electrochemical impedance spectroscopy

Solid oxide fuel cells (SOFC) for mobile applications are developed and investigated at the German Aerospace Center (DLR) in Stuttgart. Therefore a light-weight stack design was developed in cooperation with the automotive industry (BMW/Munich, Elring-Klinger/Dettingen, ThyssenKrupp/Essen) and the Research Center Jülich (FZJ). This concept is based on the application of stamped metal sheet bipolar plates, into which the SOFC cells are integrated by brazing technology. For the development and the investigation of the SOFC cells and short stacks, the electrochemical impedance spectroscopy (EIS) is an important and useful characterization method. The paper concentrates on the investigation and on the electrochemical testing of the SOFC short stacks with sintered anode-supported cells (ASC). The short stacks were electrochemically characterized mainly by electrochemical impedance spectroscopy, by current-voltage measurements and by long-term measurements. The cells and stacks were operated at different temperatures, varying fuel gas compositions, different fuel gas flow rates and at different electrical current loads. The influence of these operating conditions on the electrochemical performance of the short stacks is outlined. The nature of losses, e.g. ohmic and the polarization resistances of the electrodes were examined and determined by fitting of the impedance spectra to an equivalent circuit.     

Influence of reduced substrate shunting current on cell performance in integrated planar solid oxide fuel cells

Two-cell arrayed integrated planar solid oxide fuel cells (IP-SOFCs) were fabricated using a robo-dispensing method. Special emphasis was placed on the influence of reduced shunting current on cell performance. The resistivity of the substrate increased according to a mixture rule of composites by adding Al₂O₃ into the substrate of partially stabilized zirconia (PSZ). This strategy, which reduces shunting current through the substrate, enhances the power output. When the amount of Al₂O₃ added was more than 26 vol%, however, the Ni anode migrated into the PSZ substrate to react with Al₂O₃, which led to performance degradation. In the case of the two-cell arrayed IP-SOFC with a 20 vol%-Al₂O₃ added to the PSZ substrate, a reduced shunting current loss improved the power density by 30% compared to that of the Al₂O₃-free substrate.     

Image analysis of the porous yttria-stabilized zirconia (YSZ) structure for a lanthanum ferrite-impregnated solid oxide fuel cell (SOFC) electrode

Image analysis and quantification were performed on porous scaffolds for building SOFC cathodes using the two types of YSZ powders. The two powders (U1 and U2) showed different particle size distribution and sinterability at 1300?°C. AC impedance on symmetrical cells was used to evaluate the performance of the electrode impregnated with 35-wt.% La_0.8Sr_0.2FeO₃. For example, at 700?°C, the electrode from U2 powder shows a polarization resistance (R_p) of 0.21?Ω?cm², and series resistance (R_s) of 8.5?Ω?cm² for an YSZ electrolyte of 2-mm thickness, lower than the electrode from U1 powder (0.25?Ω?cm² for R_p and 10?Ω?cm² for R_s) does. The quantitative study on image of the sintered scaffold indicates that U2 powder is better at producing architecture of high porosity or long triple phase boundary (TPB), which is attributed as the reason for the higher performance of the LSF-impregnated electrode.     

Electrochemical characterization of vacuum plasma sprayed thin-film solid oxide fuel cells (SOFC) for reduced operating temperatures

This paper focuses on the electrochemical characterization, such as current–voltage measurements, impedance spectroscopy and long-term operation of completely plasma-sprayed SOFC assemblies for a planar metallic substrate-supported thin film concept. The influence of the variation in operating conditions is presented. To determine the different resistances in the cells, the measured impedance spectra were fitted to an equivalent circuit. This enables further improvement of the electrochemical performance of the cells and allows the assembling of high performance SOFC stacks.     

管式固体氧化物燃料电池机理模型与性能分析

针对Siemens-Westinghouse公司阴极支撑型(AES)管式固体氧化物燃料电池,耦合电极内部离子传导、电子传导、气体扩散、热量传递及电化学反应过程,建立了全面考虑活化极化、欧姆极化与浓差极化损失的管式SOFC横截面方向二维微观机理模型。模型计算结果与文献中实验数据吻合较好,模拟结果表明：电池横截面方向的组分浓度和电流密度的分布与SOFC的运行工况密切相关。连接器的存在和尺寸对电池工作性能均有较强影响。对于所研究的阴极支撑型SOFC,电池性能会受到氧气在多孔阴极中扩散过程的限制,改善多孔电极的微观结构可有效提高电池运行性能。     

Processing and performance of solid oxide fuel cell with Gd-doped ceria electrolyte

Fuel Cell performance was measured at 792-1095 K for Ni-GDC (Gd-doped ceria) anode-supported GDC film (60 μm thickness) with a (La_0.8Sr_0.2)(Co_0.8Fe_0.2)O₃ cathode using H₂ fuel containing 3 vol% H₂O. A maximum power density, 436 mW/cm², was obtained at 1095 K. The electrical conductivity of GDC electrolyte in N₂ atmosphere of 10⁻¹⁵-10⁰ Pa oxygen partial pressures (Po₂) at 773-1073 K was independent of Po₂, which indicated the diffusion of oxide ions. The conductivity of GDC in H₂O/H₂ atmosphere increased because of the further formation of electrons due to the dissociation of hydrogen in GDC (H₂ → 2H⁺ + 2e⁻). The hole conductivity was observed at 873 K in Po₂ = 10⁰-10⁴ Pa. The key factors in increasing power density are the increase of open circuit voltage and the suppression of H₂ fuel dissolution in GDC electrolyte. These are controlled by the cathode material and Gd-dopant composition.     

Novel and high-performance (La,Sr)MnO3 based composite cathodes for intermediate-temperature solid oxide fuel cells

The rapid decrease of the electrocatalytic activity at low temperature (<700 ℃) limits the popularization and application of the classical cathode material LSM (Sr doped LaMnO₃) in SOFC. Herein, we report that the introduction of CBO (CuBi₂O₄) oxide could not only reduce the sintering temperature of LSM-based cathode, but also significantly improves its electrochemical performance at intermediate temperature range of 500–700 ℃. The polarization resistance (R_p) of LSM-CBO20 (including 20 wt. % CBO) composite cathode on GDC electrolyte is only 0.13 Ω cm² at 700 ℃, which is significantly lower than the LSM cathode. The study found that the quite promoted oxygen surface exchange kinetics and catalytic activity of CBO, and the much reduced sintering temperature of the composite cathode contribute to the dramatic decrease of R_p. In addition, when Gd_0.1Ce_0.9O_1.95 (GDC) is introduced, the polarization resistance is further reduced to 0.11 Ω cm² at 700 ℃. The maximum power density of the single cell with LSMGDC-CBO20 triadic phase cathode reaches to 1460 mW cm^-2 at 700 ℃. The present study demonstrates that introducing CBO is an effective and promising approach to improve the electrochemical performance of conventional LSM-based cathode at reduced temperatures.     

Telescopic projective Adams multiscale modeling of electrochemical reactions in tubular solid oxide fuel cells

In order to predict the electrochemical performance of Solid Oxide Fuel Cells (SOFCs), a telescopic projective Adams (TPA) multiscale simulation method is proposed in this work. This method is constructed on the basis of the equation-free method (EFM). A lattice Boltzmann model is used as the fine-scale simulator of the proposed method. The electrochemical reaction-diffusion process was simulated by the TPA and the lattice Boltzmann method (LBM). The results of the two methods were found to be in good agreement, and the TPA method can give accurate results with lower computational costs. The electrochemical reactions were also simulated based on the TPA method. The results were consistent with the experimental data, indicating that the proposed TPA method is an effective tool to simulate the electrochemical reactions of SOFCs. Also, the proposed method is suggested to be helpful in multiscale modeling of other energy systems.